The invention relates to a heat exchanger, particularly for motor vehicles.
In heat exchangers of the design known for example from DE-C 23 65 476 or also DE-A 24 48 332 (corresponding to U.S. Pat. Nos. 4,305,459 and 4,159,741, respectively, which are hereby incorporated by reference), the heat exchanger consists of two water or collecting tanks between which ribbed tubes are arranged, the tubes being held and sealed in so-called collars or passages in a metal tube plate. Sealing is effected by mechanically expanding the tubes relative to the collars in the tube plate. These collars are formed from the sheet metal plate, which may consist of aluminum, steel or other metals, by punching or stamping.
In another design of heat exchangers of the same generic type, according to DE-A 21 29 096 or DE-A 19 62 466 (corresponding to U.S. Pat. No. 3,628,603, which is hereby incorporated by reference) or DE-A-17 51 710 (corresponding to U.S. Pat. No. 3,583,478 which is hereby incorporated by reference), a rubber seal is arranged between the tubes and the collars in the tube plate, and the tubes are sealed relative to the collars by mechanical expansion.
While heat exchangers of the design mentioned have so-called round tubes, that is to say tubes of circular cross section, and correspondingly shaped collars, heat exchangers having so-called oval tubes, that is to say tubes having an elliptical or practically elliptical cross section, have also been made known (DE-A 35 05 492 and EP-A 0 387 678), in which case rubber seals are also arranged between the tubes and the collars of a metal plate and the tubes are mechanically expanded.
All these designs have the common feature that the collars point only in one direction, that is to say are directed either towards the air side, i.e. towards the network, or towards the water or liquid side, i.e. towards the collecting or distribution tank.
In the course of the increasing of the power of heat exchangers of this kind the need arises to arrange the tubes, whether they are round or oval tubes, more closely side by side, that is to say with the closest possible spacing. However, limits imposed by manufacture and materials are then soon reached because a minimum distance must be maintained between the walls of two collars if it is to be possible at all to form the collars from the plate.
The underlying problem addressed by the present invention is that of providing heat exchangers of the type first mentioned above which have a higher power and in particular closer tube spacing.